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<p>A method to inhibit undesirable sexual maturation using photoperiod manipulation was studied. Under-yearling (10-month-old) masu salmon (<i>Oncorhynchus masou</i>) smolts were reared under three light regimes in fresh water from summer (August 2019) to autumn of the following year (September 2020) in the following groups: simulated natural photoperiod (SNP group), constant long photoperiod at light/dark (LD) 16:8 (LP group), and alternating photoperiod between long (LD 16:8, from August to October 2019 and from April to July 2020) and short (LD 8:16, from October 2019 to April 2020) ones (LSP group). Rearing under a constant long photoperiod (LP group) strongly inhibited the gonadal maturation. Gene expression of the two pituitary gonadotropins, namely the follicle-stimulating hormone (Fsh) and luteinizing hormone (Lh), beta subunits (<i>fshb</i> and <i>lhb</i>), and serum levels of sex steroids were low in the LP group. In contrast, the majority of individuals of the SNP and LSP groups started vitellogenesis and spermatogenesis, and upregulations in pituitary <i>fshb</i> and <i>lhb</i> as well as increased plasma sex steroid levels were observed. Thus, it is evident that SNP and LSP induced sexual maturation. On the basis of our results, a constant long photoperiod could be tested in masu salmon aquaculture to minimize the incidence of sexual maturation.</p>

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Year-round long photoperiod (LD 16:8) suppresses sexual maturation in masu salmon (Oncorhynchus masou)

  • 期刊论文

  • 发表日期：

    2025年3月7日

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  • Yuichi Ozaki,
  • Hiroshi Suzuki,
  • Toshiya Yamaguchi,
  • Yukinori Kazeto,
  • Daisuke Izumida,
  • Tomiyoshi Togawa,
  • Koichi Okuzawa

摘要

A method to inhibit undesirable sexual maturation using photoperiod manipulation was studied. Under-yearling (10-month-old) masu salmon (Oncorhynchus masou) smolts were reared under three light regimes in fresh water from summer (August 2019) to autumn of the following year (September 2020) in the following groups: simulated natural photoperiod (SNP group), constant long photoperiod at light/dark (LD) 16:8 (LP group), and alternating photoperiod between long (LD 16:8, from August to October 2019 and from April to July 2020) and short (LD 8:16, from October 2019 to April 2020) ones (LSP group). Rearing under a constant long photoperiod (LP group) strongly inhibited the gonadal maturation. Gene expression of the two pituitary gonadotropins, namely the follicle-stimulating hormone (Fsh) and luteinizing hormone (Lh), beta subunits (fshb and lhb), and serum levels of sex steroids were low in the LP group. In contrast, the majority of individuals of the SNP and LSP groups started vitellogenesis and spermatogenesis, and upregulations in pituitary fshb and lhb as well as increased plasma sex steroid levels were observed. Thus, it is evident that SNP and LSP induced sexual maturation. On the basis of our results, a constant long photoperiod could be tested in masu salmon aquaculture to minimize the incidence of sexual maturation.